Automatic straightening machines have been employed for linear cylindrical workpieces wherein deflecting rollers are programmed to deflect the workpiece beyond yield and gradually relax the deflection while the workpiece is rotating. In such case the deflecting rollers must be retracted for loading each workpiece and a driving chuck is normally employed to grasp and rotate the workpiece.
Linear machines have also been employed for straightening, thread rolling and similar operations wherein deflecting or forming linear tooling causes the workpiece to roll during advance movement of a slide actuated by a hydraulic cylinder or the like. At the end of the full stroke, the straightened or formed parts roll out and the slide is retracted to a position for loading the next part. The closest prior art known to applicant is a machine for straightening pipe disclosed in U.S. Pat. No. 2,550,842 wherein pipe is rolled by a drum having axially spaced deflecting rolls against intermediate fixed bearing shoes uniformly radially spaced concentrically from the circumference of the straightening rolls by a distance sufficiently less than the outside diameter of the pipe that a straight pipe length passing between the rolls and the bearing shoes is bent approximately to its elastic limit. A pipe length that is not straight is thus bent beyond its elastic limit sufficiently so that its elasticity straightens it as it emerges from the machine. Since the arc of the bearing shoes is concentric with that of the straightening rolls, the pipe diameter, wall thickness and heat treatment relative to elastic limit must be accurately matched to the uniform deflection in order to achieve accurate straightening.